The JB Industries LED Backlit Gauges, No. M2-820L and M2-825L, off an illuminated gauge face for legibility in dark environments. The 3-1/8" gauges feature a sturdy metal case, have an accessible on/off rocker switch and are assembled in the United States. The replaceable 3V lithium coin-cell battery provides an average battery life of more than 250 hours. Both the compound (M2-820L) and pressure (M2-825L) gauges are available for the two-valve Patriot, four-valve Zeppelin and four-valve Revolver manifolds.